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I do not use the original charger for complete charging, but only now and then for the longer balancing. Theoretically, it would take 1.5 hours longer than before with the original 3A charger, assuming that the 450wh battery pack is really completely empty, which is not the case.

1800wh (20A) Battery pack > charging with 3A >   20A / 3A = 6:40 hours
450wh (5A) Battery pack > charging with 3A >   5A / 3A = 1:30 hours
2250wh (25A) Battery pack > charging with 3A >   25A / 3A = 8:20 hours

This is only a rough calculation, because the charge current decreases towards the end and depending on the difference of the cell voltage of the individual cells, the balancing takes different times. Likewise, it should be noted again that the battery is never completely empty and no 2250wh/25A must be recharged.

When I am in a hurry I use my 9A charger and am done with a complete charge in 2:45 hours
2250wh (25A) Battery pack > charging with 9A >   25A / 9A = 2:45 hours

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On 1/23/2021 at 1:39 AM, EUC Custom Power-Pads said:

I do not use the original charger for complete charging, but only now and then for the longer balancing. Theoretically, it would take 1.5 hours longer than before with the original 3A charger, assuming that the 450wh battery pack is really completely empty, which is not the case.

1800wh (20A) Battery pack > charging with 3A >   20A / 3A = 6:40 hours
450wh (5A) Battery pack > charging with 3A >   5A / 3A = 1:30 hours
2250wh (25A) Battery pack > charging with 3A >   25A / 3A = 8:20 hours

This is only a rough calculation, because the charge current decreases towards the end and depending on the difference of the cell voltage of the individual cells, the balancing takes different times. Likewise, it should be noted again that the battery is never completely empty and no 2250wh/25A must be recharged.

When I am in a hurry I use my 9A charger and am done with a complete charge in 2:45 hours
2250wh (25A) Battery pack > charging with 9A >   25A / 9A = 2:45 hours

Did you had a extra bms or did you just add the extra batteries. My question is if you dont add another bms and just extend th battery pack like adding more cell with that do any harm

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3 hours ago, EUC Custom Power-Pads said:

Yes I have a extra BMS which you can see on the picture, because the balancing wires are all on the extra battery pack (splited into 3 pieces) 

Well my question is if i was just to add more cells to that battery pack i wont need to add a bms like if i was connecting more cells together 

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55 minutes ago, Staxkz5z6 said:

Well my question is if i was just to add more cells to that battery pack i wont need to add a bms like if i was connecting more cells together 

Rofl if I'm understanding your question right--you absolutely cannot just add cells to an existing pack, the number of cells in each pack determines the pack voltage which must correspond to the rated voltage capabilities of the rest of the wheel's electrical components (mainboard, wiring, etc). 84v wheels need pack sizes of 20 cells; 100.8v wheels need pack sizes of 24 cells; etc.

Based on the level of understanding evidenced by this question you should NOT be attempting battery modifications of any kind.

Edited by AtlasP
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2 hours ago, AtlasP said:

Rofl if I'm understanding your question right--you absolutely cannot just add cells to an existing pack, the number of cells in each pack determines the pack voltage which must correspond to the rated voltage capabilities of the rest of the wheel's electrical components (mainboard, wiring, etc). 84v wheels need pack sizes of 20 cells; 100.8v wheels need pack sizes of 24 cells; etc.

Based on the level of understanding evidenced by this question you should NOT be attempting battery modifications of any kind.

Im not trying to do any im just asking questions and but ice seen it done penlty of times and no issues with out wothout ms to scooters and unis no issues where. But mines is getting modded aith a 25a bms with bluetooh just incase 

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Well technically you can just add cells (for more capacity) to your old pack and use the same balance lead that is going to the existing string. Just depends how many cells you want hanging off each string. Most EUC's have 3 or 4 already. I wouldn't want more than that personally, but it's up to you.

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2 hours ago, Planemo said:

Well technically you can just add cells (for more capacity) to your old pack and use the same balance lead that is going to the existing string. Just depends how many cells you want hanging off each string. Most EUC's have 3 or 4 already. I wouldn't want more than that personally, but it's up to you.

Thanks for the info ive seen a few friends do it a year later dtill no issues but i added the cells and s bluetooth bms

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I wonder if it's possible to melt the balance leads by trying to hook up an external pack to an existing pack's bms? It would seem that if the discharge characteristic isn't the same between both packs, currents will flow through the balance leads under charge/discharge. Those currents can be quite large can't they? The question is, do they exceed the max 2-3A that a common 22awg balance wire can sustain?

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10 minutes ago, alcatraz said:

I wonder if it's possible to melt the balance leads by trying to hook up an external pack to an existing pack's bms? It would seem that if the discharge characteristic isn't the same between both packs, currents will flow through the balance leads under charge/discharge. Those currents can be quite large can't they? The question is, do they exceed the max 2-3A that a common 22awg balance wire can sustain?

If the "main" wiring of the external pack is sufficient balance leads should be really just for "balancing" and measurement.

Higher currents by this balance leads are a sign for somethings wrong with the cells, or as written above the main wiring along the series of cells has problems...

And of course this is for as similar as possible "selected" cells - they more they differ (cycles, brand, nominal capacity..) the higher such balancing currents could get...

In a perfect setup with perfectly selected, equal cells and perfect "main, serial" wiring these balance leads would be without any current - just for measuring and the passive balancing during charging.

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My point is that you shouldn't risk shorting the pack and possibly create a fire hazard just because the packs discharge a bit differently (but within the cells specced deviations).

My guess is that the currents wont be nearly high enough but would I let a friend or customer ride a wheel I modded like that? Maybe not...

The chinese don't daisy chain packs together to save on bms costs (tesla 1500Wh excluded). I wonder if it's for this reason.

Edited by alcatraz
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  • 2 weeks later...
On 1/28/2021 at 5:59 PM, alcatraz said:

I wonder if it's possible to melt the balance leads by trying to hook up an external pack to an existing pack's bms? It would seem that if the discharge characteristic isn't the same between both packs, currents will flow through the balance leads under charge/discharge. Those currents can be quite large can't they? The question is, do they exceed the max 2-3A that a common 22awg balance wire can sustain?

At least, if a charger with CC/CV is working normally, it will balance by charging and discharging with a current of 500ma-1A. So the balancing wire is not a big problem.

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  • 2 weeks later...
On 1/28/2021 at 3:59 AM, alcatraz said:

I wonder if it's possible to melt the balance leads by trying to hook up an external pack to an existing pack's bms? It would seem that if the discharge characteristic isn't the same between both packs, currents will flow through the balance leads under charge/discharge. Those currents can be quite large can't they? The question is, do they exceed the max 2-3A that a common 22awg balance wire can sustain?

So if hookup an external pack to the same bms but all battery packs fully charged and balanced it shouldn't be a problem?

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I don't know.

If a cell group ages in one pack but not the other, then a current will flow through the balance lead during riding and charging.

Charging is unlikely to cause a problem. (fast charging = who knows) 

It's discharging I'm a bit worried about. As the packs age (unevenly) more and more currents will flow through the leads during riding. What if they exceed the max for that balance lead?

I'd love for someone to say that those currents are miniscule and pose no risk, but I don't know that yet. I would like to know. :)

Edited by alcatraz
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On 2/20/2021 at 9:23 AM, Staxkz5z6 said:

So if I hookup an external pack to the same bms but all battery packs fully charged and balanced it shouldn't be a problem?

It won't be a problem during assembly.

It will be a problem later in the EUC's life.

You're adding undetectable failure modes. If one of your new balancing wires becomes open due to heating / desoldering, you won't be able to tell, and the EUC will seem to operate normally. Imbalance and overdischarge will then increase over time, and are likely to result in heating and cell runaway. :(

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